U.S companies and government agencies can learn from the large-scale disruptions that have simultaneously hit several banks and media outlets in South Korea in the last 24 hours.

Early analyses by security firms suggest that the attacks were carried out using previously known vulnerabilities and exploits.

So while considerable attention is being paid to whether or not North Korea is behind the targeted attacks, the real lesson is that organizations have to address the vulnerabilities that leave them exposed, security analysts said.

"It really doesn't matter if the attacker is a nation-state or a cybercriminal or a hacktivist or a bored teenage kid," said John Pescatore, director of emerging security trends at the SANS Institute in Bethesda, Md. "You have to make sure you are at least at the due-diligence level for the well-known critical security controls. If you close the well-known vulnerabilities, you can stop any attacker using those techniques."

At least three broadcast networks and four major banks in South Korea reported moderate to severe disruptions earlier today.

A report in the New York Times quoted South Korea's Financial Services Commission as saying that two banks, NongHyup and Jeju, were temporarily paralyzed after several computers were infected with a virus that deleted data from their systems.

Services at Shinhan Bank, South Korea's fourth largest financial institution, were also disrupted while a fourth financial services firm said it was hit but suffered no damage.

Meanwhile an official from South Korea's Communication Commission told the Voice of America (VoA) that the disruptions at the media operations appear to have been caused by a virus that was distributed as a software update by a patch management system. The virus basically destroyed the master boot record (MBR) on computer hard drives, causing them to crash, according to the official quoted by the VoA.

In a blog post today, security firm Kaspersky said that its analysis indicated that attackers going by the handle "Whois Team" had used a previously known "Wiper"-style malware program to wipe data on infected computers. The malware is similar to last year's Shamoon malware, which was used to destroy more than 30,000 computers at Saudi oil giant Saudi Aramco.

Meanwhile, security firm Avast Software noted in a blog that its analysis of the attacks show that they originated from a legitimate South Korean website belonging to the Korea Software Property Right Council (SPC). According to the company, the attackers appear to have exploited a previously known Internet Explorer vulnerability (CVE-2012-1889) to infiltrate computers at the affected banks.